Boris Johnson appears to have approved a plan to shut down the UK Parliament two weeks before publicly announcing it, a Scottish court has been told.
The Court of Session heard that the prime minister was sent a note on 15 August asking if he wanted to prorogue parliament from mid-September.
A tick and the word "yes" was written on the document.
The PM announced on 28 August that he wants to shut down Parliament for five weeks from next week.
He would then set out his legislative plans in a Queen's Speech on 14 October. The government insists this will give MPs sufficient time to debate Brexit before the UK's departure on 31 October.
A cross-party group of parliamentarians headed by SNP MP Joanna Cherry and Liberal Democrat leader Jo Swinson wants Scotland's highest civil court to rule that Mr Johnson has acted illegally and unconstitutionally by proroguing Parliament ahead of the UK leaving the EU.
Mr Johnson declined to give a sworn statement to the court setting out his reasons for shutting down parliament. The UK government argues that proroguing Parliament is a political decision and that the courts should not be involved.
The judge, Lord Doherty, heard from both sides in the case on Tuesday, and will deliver his ruling at 10:00 on Wednesday.
The parliamentarian's lawyer, Aidan O'Neill QC, told Lord Doherty that one of the documents produced in the case was a note sent by the government's director of legislative affairs, Nikki Da Costa, to the prime minister and his special advisor Dominic Cummings on 15 August.
Mr O'Neill said the note was headed "ending the session", and asked: "Are you content for your PPS (principal private secretary) to approach the palace with the request for prorogation to begin with the period 9 September to Thursday 12 September and for the Queen's Speech on 14 October?"
Beside that paragraph was a handwritten tick and the word "yes", Mr O'Neill added.
The QC said: "One presumes this is a document which was sent in the red box to the prime minister for him to read at his leisure in the evening of 15 August in which he says 'yes' to approaching the palace with a request for prorogation."
He added: "That appears to be developing government policy as of 15 August, but this court was told nothing of that (by UK government lawyers) and was told in fact that this judicial review is academic, hypothetical and premature.
"That is not true. This court and these petitioners were being actively misled."
He also highlighted comments in a handwritten note, understood to be from Mr Johnson, which was dated 16 August and which described the September session of Parliament as a "rigmarole introduced to show the public that MPs were earning their crust" and that he did not see "anything especially shocking about this proposition".
The note also said: "As Nikki notes, it is over the conference season so that the sitting days lost are actually very few."
Mr O'Neill said that the UK government had only sent him the notes at 22:55 on Monday - which he said was "long past my bed time" - after saying last week that they would not be be lodging any further documents.
He said the fact that the prime minister had declined to give a sworn affidavit to the court meant it "can and should draw adverse inferences".
And he argued that Mr Johnson had chosen not to be accountable to either the court or to Parliament - and that the prime minister's intention is to facilitate a no-deal Brexit.
Mr O'Neill is seeking an interim interdict - the Scottish equivalent of an injunction - on the proroguing of Parliament.
Court of Session case: How we got here
- 22 July - It emerges that a cross-party group of MPs and peers plans legal action to prevent Parliament being "closed down" in the run-up to Brexit
- 13 August - The group go to the Court of Session in Edinburgh and Lord Doherty agrees to hear arguments from both sides in September
- 28 August - The parliamentarians seek an interim interdict to block Boris Johnson' move to prorogue Parliament
- 29 August - Lord Doherty hears four hours of argument from both sides
- 30 August - The judge refuses an interim interdict but brings the full hearing forward to 3 September.
The UK government's lawyer, David Johnston, later argued that proroguing Parliament is a political decision for the government, rather than a legal matter for the court to decide.
Mr Johnston said: "This is political territory and decision making which cannot be measured against legal standards, but rather only by political judgements which must permit a degree of flexibility according to circumstances."
He said the parliamentarians behind the case had claimed that MPs were being denied the opportunity to scrutinise the government to the extent that it wishes, and to pass legislation related to Brexit.
But he said Parliament would be able to sit "for certain periods" before 31 October, and the case was therefore "academic" because "the constitutional fear that the petitioners raise has been addressed by Parliament itself, in deciding when it wishes to sit".
He also said the statute books did not set out mandatory periods when Parliament must sit, or for how long it must sit, adding: "It simply doesn't provide a legal standard to measure whether a decision to advise the Queen to prorogue Parliament is lawful or not."
Lord Advocate James Wolffe QC - Scotland's top law officer - has been given permission by the judge to take part in the hearing.
Mr Wolffe is expected to argue that the suspension of Parliament prevents scrutiny of the government's plans and represents an abuse of executive power.
As well as the Court of Session hearing, former prime minister Sir John Major and campaigner Gina Miller have joined forces to oppose the decision to suspend Parliament in the English courts.
And in Northern Ireland, proceedings have been launched at the High Court in Belfast by prominent Troubles victims' campaigner Raymond McCord - who claims that leaving the EU without a withdrawal agreement would be an "unconstitutional attack on the people of Northern Ireland"
Mr McCord is also seeking a ruling that the prime minister cannot "bypass" MPs by proroguing parliament. His case is due to call again on Wednesday.
Prorogation in a nutshell
Parliament is normally suspended - or prorogued - for a short period before a new session begins. It is done by the Queen, on the advice of the prime minister.
Parliamentary sessions normally last a year, but the current one has been going on for more than two years - ever since the June 2017 election.
When Parliament is prorogued, no debates and votes are held - and most laws that haven't completed their passage through Parliament die a death.
This is different to "dissolving" Parliament - where all MPs give up their seats to campaign in a general election.
The last two times Parliament was suspended for a Queen's Speech that was not after a general election the closures lasted for four and 13 working days respectively.
If this prorogation happens as expected, it will see Parliament closed for 23 working days.
MPs have to approve recess dates, but they cannot block prorogation.